1. Field of the Invention
This invention relates to a liquid spray pump of the type comprising: [a] a jacket, defining a longitudinal axis, [b] a piston, for being inserted, at least partially, in the jacket, and which is adapted for being moved in the direction of the longitudinal axis along the jacket, [c] at least one annular lip, surrounding a section of the piston perpendicular to the longitudinal axis, and [d] a hollow internal space defined between the jacket and the piston.
2. Prior Art Reference
Spray pumps of the type indicated hereinabove are known. They are used in a multiplicity of applications for manual pumping of more or less viscous liquid products, the pump being actuated by a push button, an operating lever, etc. They are generally used for cleaning products, do-it-yourself products, cosmetics, gardening products, etc. These pumps are usually made of plastics materials, such as, for example, polythene and polypropylene, whereby they may be more or less sensitive to the products being pumped, particularly if such products contain aggressive elements, organic solvents, gels, lacquers or other compounds which may alter the properties of the plastics forming the pump. Particularly, these spray pumps are usually provided with annular lips which form a tight seal between the piston and the wall of the jacket surrounding the piston. Simultaneously, these annular lips serve as a guide for the piston in its longitudinal movement along the surrounding jacket. These lips are particularly sensitive to aggression and, if degraded as a result of such aggression, they may cease to operate correctly in their guide function for the piston.
It is an object of the invention to overcome this drawback. This object is achieved with a liquid spray pump of the type first mentioned above in which the piston is provided with at least one shoulder occupying at least in part the hollow internal space.
In fact, in a pump of this type, the piston is guided by the shoulders. These shoulders do not provide for the liquid tightness, but only for the guiding, whereby they may be designed more strongly so that the aggressivity of the liquid does not have any appreciable influence on the guiding capacity of the shoulders.
Between the piston and the jacket there is usually a hollow internal space serving for various functions: liquid passage, removal of air during the priming of the pump, etc. One preferred solution of the invention is achieved by inserting slots between the shoulders allowing the establishment of a communication through which a fluid may flow.